No twilight

One of the coolest things about my (not so) little town of Bellingham is that we have no astronomical twilight during the week of the Summer Solstice. This means that even at 1 AM (thanks to Daylight Savings, our astronomical twilight will be at 1:12, the 12 minutes is due to not being in the dead center of our time zone) some of the sun's rays are still showing for that week. it is a really cool experience I recommend everyone see at least once, and the midnight walks are really fun.

No night on Summer Solstice

This made me think, there is no page I can find which says how far north you have to be in order to have no sunset, so I am going to write it here, by working backwards.

Furthest north locations with night every night of the year:

• 48 25' - Mount Vernon, Washington
• 48 33' - Bow, Washington

Furthest south locations with no night on summer solstice.

• 48 35' - International Falls, Minnesota
• 48 37' - Alger, Washington
• 48 45' - Bellingham, Washington

This means the answer must be 48 degrees 34 minutes to have no astronomical twilight on the summer solstice.

No Astronomical Twilight on Summer Solstice

Let's say no night is not good enough for you, you want to have no astronomical twilight as well. This will mean the horizon will be faintly visible on your summer solstice. For this, let's do another exploration:

Furthest north locations with astronomical twilight on every night of the year:

• 54 18' - Prince Rupert, British Columbia 
• 54 28' - Perry Vale, Alberta
• 54 32' - Fawcett, Alberta
• 54 34' - Kitselas, British Columbia

Furthest south locations with no astronomical twilight on summer solstice: 

• 54 35' - Boyle, Alberta
• 54 37' - Colinton, Alberta
• 54 43' - Athabasca, Alberta
• 55 10' - Grande Prairie, Alberta
• 55 41' - Chetwynd, British Columbia

You have to be further north than 54 34' in order to have no astronomical twilight on Summer Solstice.

No Nautical Twilight on Summer Solstice

But that's not enough, and you want to be able to have no nautical twilight as well on your Summer solstice, which means you will have civil twilight which means that the light will be enough to discern objects.

Furthest north locations with nautical twilight on every night of the year:

• 60 10' - Teslin, Yukon
• 60 29' - Little Teslin Lake, Yukon
• 60 32' - Sterling, Alaska
• 60 33' - Kenai, Alaska

Furthest south locations with no nautical twilight on summer solstice:

• 60 36' - Drift River, Alaska
• 60 43' - Whitehorse, Yukon

If I had to take a guess, I'm expecting that you would have to be north of 60 34' in order to have no nautical twilight.

No Astronomical Twilight on the Summer Solstice

The pattern continues further with 66 degrees, 33 minutes, and 47.5 seconds is the most famous of all these lines. The Arctic Circle, the point where locations famously have the midnight sun.

On the other hand, if you check out Rovaniemi you will find that it has no sunset at all, and is located at 66 degrees 30 minutes. so, it is time to do the same thing to find the true Arctic Circle:

Furthest north locations with nautical twilight every night of the year:

• 65 35' - Kuivaniemi, Finland
• 65 41' - Maksniemi, Finland
• 65 44' - Kemi, Finland

Furthest south locations with no sunset on the summer solstice:

• 65 46' - Savast, Sweden
• 65 48' - Karlsborg, Sweden
• 65 49' - Kaakamo, Finland
• 65 51' - Tornio, Finland
• 66 30' - Rovaniemi, Finland

Looks like the real Arctic Circle should be at 65 45' North, not where it is traditionally put.

Northernmost places with Daylight every day of the year:

The other issue, is that at the Winter Solstice, you will still have daylight at the Arctic Circle. It doesn't last long, but it is still there.

Northernmost places with daylight every day of the year:

• 67 17' - Kolari, Finland
• 67 21' - Straumen, Norway

 Southernmost places with no daylight on the Winter solstice:

• 67 24' - Andkilen, Norway
• 67 26' - Junosuando, Sweden
• 67 29' - Kango, Sweden

It looks like you have to be around 67 22 or so in order to have truly no daylight on the Winter Solstice

Southernmost places with no Civil Twilight on the Winter Solstice

But, being a vampire you really hate the light, and the civil twilight still bothers you. You have to go even further north.

Northernmost places with civil twilight on Winter Solstice:

•  71 32' - Nuugatsiaq, Greenland

Southernmost places with no civil twilight on the Winter Solstice:

• 72 42' - Pond Inlet, Nunavut
• 72 47' - Upernavik, Norway

There is a real lack of locations between these two longitudes, being in the high Arctic.

Southernmost places with no Nautical Twilight on the Winter Solstice:

Most polar places with Nautical Twilight on the Winter Solstice:

• 78 13' - Longyearbyen, Norway
• 78 31' - Minna Bluff - Antarctica

Least polar places with no Nautical Twilight on Winter Solstice:

• 78 37' - Mount Slaughter, Antarctica
• 78 39' - Mount Atkinson, Antarctica
• 78 47' - Isachsen, Nunavut
• 79 59' - Eureka, Nunavut

Southernmost places with no Astronomical Twilight on the Winter Solstice

You HATE the sun. You want dark. For a full 24 hours. And when you say 24 hours you want a full darkness uninterrupted by the sun with not even astronomical twilight.

Most polar places with Astronomical twilight on the Winter Solstice:

• 82 31' - Alert, Nunavut 
• 83 10' - Holland Range, Antarctica 
• 84 15' - Commonwealth Range, Antarctica  
• 84 30' - Hughes Range, Antarctica

Least polar places with no Astronomical twilight on the Winter Solstice, meaning it is completely pitch black, without not even a hint of the rays of the sun:

• 84 44' - Queen Alexandra Range, Antarctica
• 85 30' - Amundsen Coast, Antarctica

The lack of locations with measurements in this area makes it hard to know exactly where the point of no astronomical sunlight on the winter solstice is.

Conclusion

The following lines of latitude are the important points for various levels of twilight at solstices:

• 48 34' - No night on Summer Solstice
• 54 34' - No astronomical twilight on Summer Solstice
• 60 34' - No nautical twilight on Summer Solstice
• 65 45' - No civil twilight on Summer Solstice
• 67 22' - No daylight on Winter Solstice
• 78 31-37' - No civil twilight on Winter Solstice
• 84 30-44' - No astronomical twilight on Winter Solstice

Latitude is from Wikipedia, twilight status is from timeanddate.com